This invention relates to improved devices for actuating a valve or other controlled element automatically in response to an earthquake, vibration, or other predetermined shock forces.
The devices of the present invention are preferably of a known type including an inertia actuated weight and an associated structure which moves relative to the weight when the assembly is subjected to shock forces, with that relative displacement then being utilized to actuate a controlled element for attaining a desired purpose such as closing off the flow of a fluid through a pipeline. Typical devices for this purpose are shown in U.S. Pat. No. 4,185,507 issued Jan. 29, 1980 to Frank M. Domyan, and in our copending application Ser. No. 381,329 filed May 24, 1982 on "Magnetically Actuable Shock Responsive Unit".
A major purpose of the present invention is to provide an improved shock responsive actuator of this general type which is capable of applying a greater force to the controlled element in the actuated condition of the unit than has been possible with most prior devices of which we are aware. For example, a mechanism embodying the invention can function to open a valve against a substantial pressure, to release compressed air or another pressurized fluid for flow through the valve to a desired location. The mechanism may also function to effectively lock the controlled element in its actuated condition until the device is purposely reset to a cocked condition. The apparatus is very simple structurally and reliable in operation and occupies relatively little space.
To achieve these results, a unit embodying the invention includes two swinging arms, one of which is latched in a predetermined position by shock responsive means and is adapted to be released for movement from that position to a second position when the unit is subjected to an earthquake or other shock forces. The second arm acts by swinging movement to actuate the valve or other controlled element, and is actuable by the first arm through a mechanical advantage linkage which swings the second arm through a smaller angle than the first arm but with greater force. This linkage desirably includes two links pivotally connected at first ends thereof to swing between angularly disposed positions and essentially aligned preferably slightly overcenter positions, with a third link connecting one or both of the first and second links to the first mentioned arm for actuation thereby. The three links are desirably connected pivotally together at a common axis.